The present invention relates to a water filtration system which can be conveniently fastened to an aquarium and controlled to let gas be admitted in minute bubbles into water and then to let treated water flow downwards to the aquarium again.
Various water filtration and aeration systems are known, and widely used in aquariums. These water filtration and aeration systems are commonly fastened to the bottom of the aquarium for letting gas be admitted in minute bubbles into water. As gas is released upwards, it escapes out of water rapidly. Therefore, much gas is wasted.